The purposes of this study were: 1) to compare mortality and postoperative morbidities in extremely low birth weight (ELBW) infants who underwent initial laparotomy or drainage for necrotizing enterocolitis (NEC) or isolated intestinal perforation (IP); 2) to determine the ability to distinguish NEC from IP preoperatively and the importance of this distinction on outcome measures; and 3) to evaluate the association between extent of intestinal disease determined at operation and outcome measures. All ELBW infants born at participating NRN centers were screened for the presence of NEC or IP that was thought by the pediatric surgeon and neonatologist to require surgical intervention. Data were collected enrolled infants, including: intraoperative findings recorded by the surgeon and specific post-operative complications. Neurodevelopmental examinations were conducted on surviving infants at 18-22 months corrected age.